Folding Machine with Suction Means for Zig-Zag Folding a Continous Web Material and Associated Folding Method

ABSTRACT

The folding machine comprises; a pair of counter-rotating folding cylinders ( 1, 3 ), each provided with at least one gripping member ( 43 ) to fold a continuous web material (N) in a zigzag manner; and a cutting member ( 60 ) disposed in front of the folding cylinders to cut the zigzag folded web material and divide it into two piles (M) of folded articles. Each gripping member is a suction member which retains the web material by suction at the level of the respective folding line.

TECHNICAL FIELD

The present invention relates to a folding machine to fold a webmaterial along transverse folding lines. More specifically, theinvention relates to a folding machine of the type comprising a pair ofadjacent counter-rotating folding cylinders having parallel axes, eachof which has at least one gripping member to grasp the web materialalong transverse lines and make folds along said lines.

The invention also relates to a means to perform folding of a continuousweb material according to transverse zigzag lines.

STATE OF THE ART

In many folding machines used in the field of paper converting toproduce, for example, folded paper napkins, a continuous webmaterial—optionally previously folded along a longitudinal line—is fedto a pair of counter-rotating folding cylinders, disposed adjacent toeach other to define a nip through which the web material passes andhaving parallel axes. Disposed on each cylinder are members that makethe fold in the web material. The aforesaid members are disposed andcontrolled so that the web material is folded in a zigzag manner,adhering alternately first to one and then to the other of the twocounter-rotating folding cylinders. The pack formed of the zigzag foldedweb material is then cut by a blade and divided into two piles of papernapkins or similar folded products.

A machine of this type is described for example in WO-A-9728076 and inWO-A-0162651. Other examples of folding machines are described in U.S.Pat. No. 3,195,882, in U.S. Pat. No. 3,229,974, in U.S. Pat. No.3,820,774, in U.S. Pat. No. 3,689,061, in German patent 4.446.753 and inGerman patent 429.288.

The folding members of these folding machines include, disposed on eachfolding cylinder, a gripping member, which grips the web material alonga folding line at each turn of the cylinder. To insert the web materialinto the gripping member, respective folding blades or wedges aredisposed on the two folding cylinders, in positions angularly staggeredwith respect to the gripping members. To make a fold a folding blade ofone of the two folding cylinders and a gripping member of the otherfolding cylinder are disposed in angular positions so that theycorrespond with each other in the nip defined between the two foldingcylinders, so that the web material is pushed by the folding bladeinside the gripping member.

Typically, each of the two folding cylinders has at least one foldingblade and one gripping member, so that for each complete turn of thepair of folding cylinders at least two folds are made on the webmaterial.

The presence of folding blades and gripping members on thecounter-rotating folding cylinders makes these machines particularlycomplex from a mechanical viewpoint. Moreover, the mechanical action ofthe folding blade or wedge on the web material tends to damage it. Thefolding blades are subject to rapid wear with consequent maintenancecosts.

Folding machines of another type and with a different configuration tothose to which the present invention relates are described in U.S. Pat.No. 5,356,131; U.S. Pat. No. 4,921,235; WO-A-03016184.

OBJECTS AND SUMMARY OF THE INVENTION

The object of the present invention is to produce a folding machine ofthe aforesaid type, which is simpler, while at the same time efficientand reliable.

This and further objects and advantages, which shall be apparent tothose skilled in the art by reading the text hereunder, are obtainedessentially with a folding machine comprising: a pair ofcounter-rotating folding cylinders, each provided with at least onegripping member to fold a continuous web material in a zigzag manner; acutting member disposed in front of said folding cylinders to cut thezigzag folded web material and divide it into two piles of foldedarticles; characterized in that each gripping member is a suction memberwhich retains the web material by suction at the respective foldingline. The continuous web material (typically and preferably tissue paperfor producing handkerchiefs or napkins and the like) is thus engagedalternately on one and on the other of the counter-rotating foldingcylinders by suction, and said suction which engages the web material inequidistant areas causes the zigzag folding thereof, without the need touse complex mechanical members to grip the material with relative cammechanisms to control them. This simplifies the machine, also making itefficient and reliable.

To facilitate folding and, optionally, to obtain particularly reliableoperation even at high speeds, according to an advantageous embodimentof the invention each of the folding cylinders can be provided with awedge element in phase with the gripping member of the opposed cylinder,to produce a line which facilitates folding in the web material, at thelevel of said gripping member. The line which facilitates folding is insubstance a sort of crease and can be obtained in a particularlyefficient way by providing, for each wedge element, a correspondingnotch produced on the opposite cylinder, associated with the suctiongripping member.

According to a different aspect, the invention relates to a method forproducing folded articles from a continuous web material, advantageouslyand preferably in tissue paper, comprising the phases of: feeding thecontinuous web material into a nip defined between two counter-rotatingfolding cylinders, each provided with at least one gripping member;folding the web material in a zigzag manner by means of said foldingcylinders, engaging the web material with the gripping members of oneand of the other of said folding cylinders alternately; feeding thezigzag folded web material towards a cutting member (60); by means ofsaid cutting member, cutting the zigzag folded web material into twopiles of folded articles; characterized in that the web material isretained and folded in said folding cylinders by suction.

Advantageously, the method can include a creasing phase of the webmaterial, preferably obtained by means of said folding cylinders.

Further advantageous characteristics and embodiments of the machine andof the method according to the invention are indicated in the appendedclaims and described in greater detail hereunder, with reference to anexample of embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention shall be better understood by following the descriptionand accompanying drawing, which shows a non-limiting example ofembodiment of the invention. In particular, in the drawing:

FIG. 1 is a plan view of a folding machine incorporating the invention;

FIG. 2 is a front view of the folding cylinders of the machine;

FIG. 3 is a plan view according to III-III in FIG. 2;

FIG. 4 is a longitudinal section of one of the folding cylinders;

FIG. 5 is a schematic cross section according to V-V in FIG. 2 of thetwo folding cylinders;

FIGS. 6A and 6B are enlargements, in two subsequent positions, of thegripping members of one of the folding cylinders in the point in whichthe folded web material starts to detach from the folding cylinder;

FIG. 7 is a section according to VII-VII in FIG. 2;

FIG. 8 is an enlargement in longitudinal section of the suction area ofone of the folding cylinders;

FIG. 9 is a plan detail of the assembly flange of the suction unit; and

FIG. 10 is an enlarged local section according to a plane orthogonal tothe axes of rotation of the folding cylinders at the level of thefolding area, in the instant in which the crease is formed on the webmaterial.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

With initial reference to FIG. 1, the folding machine has a pair offolding cylinders 1 and 3 rotating according to the arrows f1 and f3around respective vertical axes of rotation 1A and 3A, disposed parallelto each other and spaced so that the two folding cylinders 1, 3 areadjacent to each other at the level of a nip 5. The folding cylinder 1is supported by shanks 1C and 1D (FIG. 2) in corresponding supports 7,9. The folding cylinder 3 is supported in a similar way by shanks 3C and3D in supports 11 and 13.

The two folding cylinders 1 and 3 are made to rotate in oppositedirections (arrows f1 and f3 in FIGS. 1, 5 and 7) by means of a toothedwheel 14 which meshes with a toothed wheel 15 keyed onto the shaft ofthe folding cylinder 1, and which in turn meshes with a toothed wheel 17keyed onto the shaft of the folding cylinder 3.

An eccentric 19 is mounted at the upper end of the shaft 1C of thefolding cylinder 1, and, by means of a connecting rod 21, provides analternate movement to a rocker 23 (see FIGS. 2 and 3). The rocker 23 iskeyed onto a vertical shaft 25, parallel to the axes of the two foldingcylinders 1, 3 and carries integral therewith three shaped bars 26 whichare inserted into corresponding annular grooves 27 of the foldingcylinder 1 (see in particular FIG. 2).

Hinged to the rocker 23, at the opposite end to the end at which theconnecting rod 21 is hinged, is a further connecting rod 29, theopposite end of which is hinged to a bracket 31 keyed onto a shaft 33,parallel to the shaft 25. Integral with the shaft 33 are three bars 35,analogous to the bars 26, which are inserted into corresponding grooves37 provided on the folding cylinder 3. The number of bars 26, 35 canvary according to the height of the folding cylinders 1, 3.

As can be seen in particular in the cross section in FIG. 5 and, limitedto the folding cylinder 3, in the section in FIG. 4, a longitudinal seator cavity, indicated as a whole for both cylinders with 41, is producedinside each of the folding cylinders 1, 3. The two cavities 41 aresymmetrical to each other as can be seen in particular in FIG. 5 and thefolding cylinders are in phase with each other so that the cavities arein diametrically opposite positions.

The cavities 41 emerge on the cylindrical surface of each of the twofolding cylinders 1, 3. Housed in each of the two seats or cavities ofeach folding cylinder 1, 3 is a gripping member, indicated as a wholewith 43, used to grasp and fold the web material N fed into the nip 5between the two folding cylinders 1, 3. The two gripping members 43 aresymmetrical to each other and only one of them shall be described indetail hereunder with particular reference to FIG. 4.

The gripping member 43 is essentially composed of a block provided witha series of through holes 45 (disposed in the example shown on four rowsparallel to the axis of the folding cylinder). The holes emerge on anessentially flat internal or rear surface 47 of the block 43 and on anessentially cylindrical outer surface 49 positioned flush with thecylindrical surface of the respective folding cylinder 3 (or 1). Thecylindrical surface 49 is interrupted at the level of the grooves 37 (or27) of the folding cylinders 1 and 3 and at the level of said annulargrooves has lowered areas 51, to allow passage of the bars 26, 35.

The seat 41 of both cylinders 1 and 3 is in connection with a suctionduct 53 extending coaxially to the axis of rotation of the respectivecylinder and emerging on the upper front surface thereof, where (asshall be described hereunder) it is carried for a certain angle ofrotation of the respective cylinder in communication with a suctionline. In this way, through the holes 45 of each block 43 a suction isproduced—for a predetermined angle—the purpose of which, as shown ingreater detail hereunder, is to temporarily retain the web material tobe folded along a transverse folding line.

On the cylindrical front surface 49 of each block 43, a cut or notch 55is produced (see enlargement in FIG. 10), into which a wedge 57,produced on an insert 59 disposed on the opposed cylinder, penetrates.As can be seen in FIG. 5, on each of the two folding cylinders 1, 3 theblock 43 and the insert 59 are disposed in diametrically opposedpositions, so that during rotation of the two cylinders 1, 3 in the nip5 each notch 55 of a block 43 mounted on one of the two cylinders comesto correspond with the wedge 57 of the insert 59 mounted on the othercylinder.

The machine described hereinbefore operates in the following way. Whenthe folding machine is operating, a web material N, optionally foldedlongitudinally upstream of the folding cylinders 1, 3 with systems knownper se and not described herein, is fed (arrow fN, FIG. 1) through thenip 5 between the folding cylinders 1, 3. Here it is engaged alongtransverse folding lines alternately by one or by the other of the twosuction gripping members composed of the blocks 43 with the relativesuction holes 45.

Suction through the holes 45 is activated, for each cylinder 1, 3 beforethe line of holes 45 farthest forward with respect to the direction ofrotation of the respective cylinder 1, 3 reaches the nip 5, so that theweb material is drawn and retained on the cylindrical surface of therespective folding cylinder. The plurality of lines of suction holes 45guarantees efficient retention of the web material when this passesthrough the nip 5 and moves therebeyond, following the movement ofrotation of the cylinder.

Suction through the holes 45 is maintained until the block 43 is in anangular position approximately 45-60° farther forward than the positionof the nip 5. In this way, the web material N, which advances atessentially the same peripheral speed as the folding cylinders 1, 3, asa consequence of suction, continues to adhere to the folding cylinder 1or 3 on which suction has been activated, producing a fold as shown inFIG. 5 (in this case the fold formed by the cylinder 3 is shown). In theposition in FIG. 5 suction has been interrupted and the folded edge ofweb material N is detached from the folding cylinder 3, facilitated inthis by the oscillatory movement of the bars 35, the oscillatingmovement of which is advantageously synchronized with the angularposition of the folding cylinders 1, 3. The fold produced by thegripping member 43 associated with the folding cylinder 3 is indicatedwith P.

Continuing rotation in opposite directions of the two folding cylinders1, 3, when the suction gripping member 43 is in proximity to the nip 5suction is activated therethrough to form a fold on the material N,analogous to the fold P produced by the folding cylinder 3.

With continual rotation of the folding cylinders 1, 3 and alternateactivation of suction through one or other of the two gripping members43, a zigzag fold is obtained on the web material N. This thus forms apack of material P which is fed (FIG. 1) according to the arrow Ftowards and against a cutting member 60 with a cutting edge parallel tothe axes of rotation 1A, 3A of the folding cylinders 1, 3 and disposedon a vertical plane tangent to the two cylinders. The cutting member canbe (in a per se known manner) a fixed or movable member and divides thepack P into two piles M1, M2 of napkins or other folded articles, whichare fed towards the unloading area of the machine, where members knownand not described in detail herein are disposed to separate theindividual packs of articles from each other.

To facilitate forming of the folds at the level of the gripping members43 wedges 57 cooperating with the notches 55 are provided. These twoelements are inserted inside each other at the level of the nip 5 (FIG.10), deforming the web material N between them. This forms a line tofacilitate folding, essentially in the form of a crease. To obtain this,it is not necessary for particularly high pressure to be exerted betweenthe two elements 55, 57. However, it is advantageous for the notch 55 tobe produced in a removable and replaceable portion of the block 43. Thisremovable portion can advantageously be made of a yielding material,such as rubber, which may be relatively hard although with greaterelasticity than the metal material of which the remaining part of theblock 43 is composed. As can be seen in the drawing, for each block 43,the notch 55 is positioned at the level of the row of suction holes 45farthest forward with respect to the direction of rotation of therespective folding cylinder 1 or 3.

To connect the suction duct 53 of each of the two folding cylinders 1, 3to the suction, for example a line connected to a fan, an arrangement isprovided of a connection cooperating with the upper front surface ofeach of the two cylinders, indicated with 1F for the folding cylinder 1and with 3F for the folding cylinder 3. This arrangement is shown indetail in FIGS. 7, 8 and 9 for the folding cylinder 3. A symmetricalarrangement is provided for the folding cylinder 1.

By means of a plate 83 in a material with a low coefficient of friction,a shoe 81 rests on the front surface 3F of the cylinder 3. The shoe 81is connected slidingly to two vertical guide columns 85 clamped inrespective sleeves 87. These are in turn fixed on a flange 89 clamped ona portion 91 of the fixed structure of the machine. Two compressionsprings 93 (one of which can be seen in FIG. 8) stress the shoe 81against the front surface of the respective folding cylinder 1 or 3.

The flange 89 is shown in a plan view in FIG. 9. Two sets of three holesof the fixing screws 97 of the sleeves 87 to retain the guide columns85, are indicated with 95. As can be seen in FIG. 9, the flange 89 isprovided with two curved slots 99. Two screws (one of which is indicatedwith 101 in FIG. 8) are inserted in these slots to fix the flange 89 tothe structure 91 of the machine. Thanks to the curved slots 99, byloosening the screws 101 the angular position of each flange 89 can bemodified with respect to the axis of the relative folding cylinder 1 or3. In this way it is possible to adjust the angular position of therespective shoe 81.

The structure of the shoe 81 is shown in detail in FIGS. 7 and 8. It hasa main body in which a lowered seat 103 is produced, inside which theplate 83 is housed. The main body and the plate 83 of the shoe 81 have ahole with an oblong section 105, which extends parallel to the axis ofthe folding cylinder 1 and 3. The oblong hole 105 is joined to a sidehole 107 connected to a suction pipe 109 in turn connected to a fan orother suitable suction member, not shown. The oblong hole 105 extendsangularly, corresponding to the angle of rotation of the cylinder 1 or 3along which suction is implemented through the holes 45 of the block 43.

With this arrangement, when the folding cylinder 1 or 3 rotates aboutthe axis thereof, suction is produced inside the suction duct 53 for theentire rotation of the cylinder to which the suction duct 53 isconnected with the oblong hole 105 produced in the shoe 81. Thepossibility to adjust the angular position of the flange 89 allowsadjustment of the angular positions in which suction starts andterminates inside the suction duct 53.

It is clear from the above description that with the suction systemassociated with the folding cylinders 1, 3 the web material N is folded(optionally with the aid of the crease line which can be produced by thewedge 57 cooperating with the notch 55) without the need for mechanicalgripping members controlled and operated by particularly complex camsystems, as is the case in conventional devices.

Compared to conventional machines (such as the type described inWO-A-0162651), the machine is consequently much simpler.

It is understood that the drawing purely shows a possible embodiment ofthe invention, which may vary in forms and arrangements without howeverdeparting from the scope of the concept on which the invention is based.Any reference numerals in the appended claims are provided for the solepurpose of facilitating reading in the light of the descriptionhereinbefore and the attached drawings and do not in any way limit thescope of protection.

1. A folding machine comprising: a pair of counter-rotating foldingcylinders (1, 3), each provided with at least one gripping member (43)to fold a continuous web material (N) in a zigzag manner; a cuttingmember (60) disposed in front of said folding cylinders to cut thezigzag folded web material and divide it into two piles (M) of foldedarticles; characterized in that each gripping member is a suction memberwhich retains the web material by suction at the level of the respectivefolding line.
 2. Folding machine as claimed in claim 1, characterized inthat each folding cylinder (1, 3) has a wedge element (57) in phase withthe gripping member of the opposed cylinder, to produce a line whichfacilitates folding in the web material, at the level of said grippingmember.
 3. Folding machine as claimed in claim 2, characterized in thatsaid wedge element (57) cooperates with a notch (55) associated with thegripping member (43) with which said wedge element is in phase. 4.Folding machine as claimed in claim 3, characterized in that said notchis produced in an interchangeable insert.
 5. Folding machine as claimedin claim 4, characterized in that said interchangeable insert isproduced in an elastically yielding material.
 6. Folding machine asclaimed in one or more of the previous claims, characterized in thateach of said gripping members (43) has at least one alignment of suctionholes (45), said alignment extending parallel to the axis (1A, 3A) ofthe respective folding cylinder (1, 3).
 7. Folding machine as claimed inclaim 6, characterized in that it has, for each gripping member, aplurality of alignments of suction holes (45).
 8. Folding machine asclaimed in claim 3 and 6, characterized in that each of said notches(55) is disposed at the level of a respective alignment of suction holes(45).
 9. Folding machine as claimed in one or more of claims 6 to 8,characterized in that said suction holes (45) of each folding cylinderare produced in a block (43) housed in a seat (41) of the respectivefolding cylinder (1, 3).
 10. Folding machine as claimed in one or moreof the previous claims, characterized in that means to synchronizesuction with the angular position of the respective folding cylinder (1,3) are associated with each of said suction gripping members (43). 11.Folding machine as claimed in one or more of the previous claims,characterized in that oscillating bars (26, 35) housed in annulargrooves (27, 37) of the respective cylinder are associated with eachfolding cylinder, to cause detachment of the folded web material fromthe folding cylinders.
 12. A method for producing folded articles (M)from a continuous web material (N) comprising the steps of: feeding thecontinuous web material into a nip (5) defined between twocounter-rotating folding cylinders (1, 3), each provided with at leastone gripping member (43); folding the web material in a zigzag manner bymeans of said folding cylinders, engaging the web material with thegripping members of one and of the other of said folding cylindersalternately; feeding the zigzag folded web material towards a cuttingmember (60); by means of said cutting member (60), cutting the zigzagfolded web material into two piles of folded articles (M); characterizedin that the web material is retained and folded in said foldingcylinders by suction.
 13. Method as claimed in claim 12, characterizedin that crease lines are produced mechanically in the web material atthe level of said gripping members, which retain the web material bysuction.
 14. Method as claimed in claim 13, characterized in that saidcrease lines for facilitating folding are produced by means of said twofolding cylinders.
 15. Method as claimed in claim 14, characterized inthat said crease lines for facilitating folding are produced byinterpenetration of a wedge element (57) and a notch (55), produced onone and on the other of said two folding cylinders, with the webmaterial (N) disposed between said wedge element (57) and said notch(55).
 16. Method as claimed in one or more of claims 12 to 15,characterized in that said web material is tissue paper.